1. Field of the Invention
The present invention generally relates to an intersection warning system, and more particularly to an intersection warning system by which a driver of a vehicle approaching an intersection is warned when another vehicle is approaching the intersection from a side direction.
2. Description of the Related Art
In the related art, an intersection warning system as disclosed in Japanese Laid Open Patent Application No.7-14099 has been proposed. In this system, when a vehicle is approaching the intersection from one direction, another vehicle approaching the intersection from another direction (from the side) is detected by a laser radar and detecting information is transmitted to the vehicle approaching the intersection from the one direction. In the vehicle which receives the detecting information, warning is issued so that a driver of the vehicle is informed of the presence of the other vehicle approaching the intersection from the side.
Meanwhile, in recent years, vehicles have been made more intelligent. To intellectualize the vehicles, for example, an obstacle detecting system and an active cruise control system (ACC system) have been proposed. In such systems, the forward area of a vehicle is watched, for example, by using radar. That is, a transmitter emits radio waves or laser beams and it is checked whether reflected waves are received by a receiver. The distance between the vehicle and an obstacle in the forward area of the vehicle is then measured based on the period between a time at which the radio waves were emitted and a time at which the reflected waves are detected.
Particularly, in the obstacle detecting system, when an obstacle is detected based on the result of watching the forward area of the vehicle, a warning is issued and/or a braking control is performed so that the vehicle stops before the obstacle. In the active cruise control system, when a forward vehicle is detected based on the result of watching the forward area of the vehicle, accelerating control and braking control are performed so that the distance between the vehicle and the forward vehicle is maintained at a constant value.
In a case where a vehicle is intellectualized, since a plurality of systems is to be provided in the vehicle, it is preferable that similar functioning units be shared by the plurality of systems.
However, in a case where a vehicle-side system (having a receiver and other units) of the conventional intersection warning system as described above is provided in a vehicle having the obstacle detecting system and/or the adaptive cruise control system, objects to be detected differ from each other between the systems. Thus, although the radio waves have to be received in each of the respective systems of the vehicle, the receiver can not be shared by the respective systems.